News

Unreleased

This is the first entry in the resumed changelog. Changes below are listed relative to 0.15.1 (released 2025-06-24); releases between the historical notes below and 0.15.1 were not tracked here.

Breaking changes

• Bazel 8 is now required for bzlmod. The primary tested Bazel version moved to 8.6.0. Bazel 7 is still supported, but only in WORKSPACE mode; if you use bzlmod you must be on Bazel 8 or newer (#1514).
• Built toolchains now ship only the latest patch of each minor series. You can request a <major>.<minor>.x wildcard (e.g. cmake_version = "3.19.x") which resolves to the newest known patch of that series. The exact-latest version string still works, but other previously-valid exact patch versions now fail (#1559).
• Several default built-tool versions changed, so unpinned users get the newer version automatically. The default built meson jumped from 1.5.1 to 1.10.1 (a five-minor jump that can change meson behavior; fixes builds under apple-clang 17 / Xcode 26) (#1473), and the default cmake (3.31.8 → 3.31.12) and ninja (1.13.0 → 1.13.2) moved with the latest-patch-per-minor change above (#1559). Pin the relevant *_version argument of rules_foreign_cc_dependencies if you need the previous version.
• Unrecognized platforms now fail the build instead of warning. An unknown target/host OS or CPU (or an unmapped processor/target-OS parameter) now errors out rather than silently falling back to a native compile. Builds that previously limped along on an unrecognized platform will need a platform-data update (#1490, building on #1438).
• Prebuilt ninja 1.8/1.9 binaries were dropped. The supported prebuilt ninja range is now 1.10 to 1.13, matching the build-from-source range. The exact 1.8.2/1.9.0 versions and the 1.8.x/1.9.x wildcards no longer resolve. If you were requesting a prebuilt 1.8/1.9 (via ninja_version or tools.ninja(version = ...)), move up to 1.10 or newer (#1565).
• The bzlmod tools extension is now hub-and-spoke. Register the single @rules_foreign_cc_toolchains//:all target instead of individual spoke targets. The version-suffixed source-archive repos (e.g. @cmake_src_3.31.12) replace the previous singleton names (@cmake_src); there is no zero-edit migration path. See Migrating to the bzlmod hub for the rename table and the two supported migration patterns (#1567).
• The per-platform binary spoke repos were renamed to one scheme, @<tool>-<version>-<os>-<arch> (e.g. @ninja_1.13.2_linux became @ninja-1.13.2-linux-x86_64, and cmake's upstream platform tokens were normalized to Bazel spellings such as windows-x86_64). These are implementation repo names; the hub and the @<tool>_<version>_toolchains aggregators are unchanged, so this only affects code that referenced a binary spoke by its literal name. See Migrating to the bzlmod hub (#1567).
• The public @rules_foreign_cc//toolchains:built_*_toolchain labels were removed (built_cmake_toolchain, built_ninja_toolchain, built_make_toolchain, built_meson_toolchain, built_pkgconfig_toolchain). The build-from-source toolchains are now per-version spokes registered through the hub. Consumers that registered these labels directly should declare the matching tools.<tool>(mode = "source", version = "...") tag (an explicit version is required), or register the spoke-provided toolchain. See Migrating to the bzlmod hub (#1567).
• The autogenerated @rules_foreign_cc//toolchains:cmake_versions.bzl data file was removed. Its CMAKE_SRCS table moved to //toolchains/private:cmake_versions.bzl as CMAKE_SRC_SRCS and is no longer publicly loadable. It was a "DO NOT MODIFY" generated data file; out-of-tree loads of it (always unsupported in spirit) must drop the dependency (#1567).

New features

• New msbuild rule for building MSBuild (.vcxproj/.sln) projects with MSBuild.exe from MSVC. Only the pre-installed toolchain is supported (#1443).
• New resource_size attribute on all build rules (default/tiny/small/medium/large/enormous, plus a fixed single-CPU serial). It declares the action's CPU/RAM footprint to the Bazel scheduler and forwards parallelism env vars (CMAKE_BUILD_PARALLEL_LEVEL, GNUMAKEFLAGS, MESON_NUM_PROCESSES, NINJA_JOBS) to the underlying build system. Defaults can be overridden via bazel run @rules_foreign_cc//foreign_cc/settings (#1465, #1511). For sized targets, the build tool may use the reserved CPU count plus 2 (tunable via --@rules_foreign_cc//foreign_cc/settings:parallelism_overcommit); serial is exempt and always runs -j1 (#1533).
• Output validation in-action via the new experimental_validate_outputs_in_action attribute (default on). When an expected installed output is missing, the build now fails with a clear message that lists nearby/similarly-named files and preserves the temp tree, instead of Bazel's opaque "output was not created" error. Disable per-target with experimental_validate_outputs_in_action = False (#1517).
• Opt-in short build paths on Windows via the --@rules_foreign_cc//foreign_cc/settings:allow_building_in_tmp flag (default off), which relocates the build tree under $TMP to stay below the 260-char MAX_PATH limit (#1527).
• set_file_prefix_map is now available on the built-tool rules (in addition to the main rules), and a new --@rules_foreign_cc//foreign_cc/settings:set_file_prefix_map_default flag turns it on globally; the per-rule attribute still wins. This strips sandbox paths via -ffile-prefix-map to improve build reproducibility (skipped on MSVC) (#1545, groundwork in #1553).
• boost_build and the built ninja tool now honor toolchain copts/linkopts (previously advertised but ignored) (#1554).
• ninja now wires up the cc toolchain's C build variables (compilers, flags, pkg-config, and dependency env) the same way make does, instead of relying on tools found on PATH. Existing ninja() targets now build with the configured toolchain (#1477).
• meson gains a shared_ldflags_option attribute that routes shared-library linker flags into a named meson build option, fixing shared_library() link failures when executable-only flags such as -pie are present; options values are now location/make-variable expanded (#1401).
• make and configure_make gain dynamic_module_ldflags_vars for loadable-module (plugin) linker flags, kept separate from shared-library flags. This is primarily for Darwin, where module links use -bundle (#1542).
• configure_make now stubs autotools regen tools (ACLOCAL, AUTOCONF, AUTOMAKE, etc.) so builds don't spuriously trigger regen recipes that break on RBE or hosts lacking those tools. The new unstubbed_regen_tools attribute lets a target opt specific tools back in (#1544).
• out_data_dirs and out_data_files contents are now exposed as output groups, so you can reference them directly instead of going through gen_dir or a genrule (#1451, #1464).
• cmake cross-compilation gains more targets: armv7 and x86_32 CPUs with OS-aware CMAKE_SYSTEM_PROCESSOR values (fixing Android armeabi-v7a/x86 builds) (#1555), iOS/tvOS/watchOS CMAKE_SYSTEM_NAME mappings (#1495), and macOS as a cross-compile target (#1438).
• cmake sets CMAKE_OSX_SYSROOT automatically on macOS from the hermetic sysroot, so cmake honors it instead of searching for Xcode (#1361).
• New noop_<tool>_toolchain targets under //toolchains (one per noop-capable build tool: cmake, ninja, make, meson, pkgconfig, autoconf, automake, m4, msbuild). nmake has no noop toolchain: it shares make's toolchain type, so tools.make(mode = "noop") no-ops the make family. Each is a tool-implementation target pointing the tool at a failing path. This is for builds that resolve a tool but treat it as optional and never invoke it (e.g. pkgconfig set to noop to disable package searches): resolution succeeds and that step is skipped. If a build does invoke a noop tool it fails loudly rather than silently falling back to a host binary. These are implementation targets (they go in the toolchain = ... field of a toolchain() rule), not directly registerable toolchains; wrap one in your own toolchain() to use it (#1567).
• Per-tool bzlmod tag classes with mode selection. Each tool takes a mode (some subset of binary, source, system, noop, depending on the tool) plus an optional pinned version. mode = "noop" selects the built-in noop_<tool>_toolchain (above), so tools.<tool>(mode = "noop") satisfies resolution without invoking the tool. Root modules can opt out of the rfcc-default registrations with tools.explicit(), or fetch a spoke without registering it via register_toolchain = False (#1567).
• cmake and ninja now register a host-PATH system toolchain in addition to their prebuilt binary. The binary toolchain still wins on the platforms rules_foreign_cc ships prebuilts for; on any other host, resolution now falls back to a cmake/ninja found on PATH instead of failing. This restores the WORKSPACE default behavior. If you relied on resolution failing on an unsupported platform, use tools.explicit() and declare only the cmake/ninja modes you want (#1567).

Bug fixes

cmake

• Default CMAKE_MSVC_DEBUG_INFORMATION_FORMAT to Embedded (/Z7) and replace /Zi, fixing intermittent "PDB API call failed" (C1090) errors when building multiple cmake targets in parallel on Windows. This changes the default debug-info format for anyone who hasn't set the cache variable explicitly (embedded in .obj rather than a separate .pdb) (#1483).

meson

• Fix the CMake-based dependency fallback by restoring the ninja wrapper name and adding make as a dependency, so meson/cmake dependency lookups resolve correctly (#1506).
• Export AR and STRIP from the cc toolchain so meson uses the hermetic archiver/stripper (#1302).
• Fix meson_with_requirements so Python modules declared as requirements are found when meson re-invokes python directly (#1487).
• A value set via target_args["setup"] is no longer clobbered by the empty deprecated setup_args, and the deprecation only fails when the deprecated arg is actually set (#1444).

Framework (applies across rules)

• $$EXT_BUILD_DEPS$$ references in user attributes are now properly escaped so they survive make-variable expansion into the generated build scripts (#1496).
• Honor --force_pic: objects are now built position-independent when the toolchain requires PIC for dynamic libraries, fixing shared-library link errors (#1440).
• Fix directory symlinks in subdirectories that produced dangling links (#1469).
• Resolve the Apple SDK root via xcrun --sdk without the deprecated APPLE_SDK_VERSION_OVERRIDE suffix, fixing builds with non-standard SDK names (#1467).
• Populate RANLIB from the toolchain when available instead of always using a no-op (:), fixing parallel builds (e.g. openssl) that need a real ranlib (#1509).
• Variant toolchain attributes (toolchain/extra_toolchain) accept select() again and extra_toolchain is now optional (#1466, fixing a regression from #1459).

Built pkg-config / make tools

• Fix building the from-source pkg-config tool on Windows (#1459), compile it with -std=gnu90 to fix failures on newer compilers (e.g. glib) (#1458), and prefer the fast mirror.bazel.build download mirror (#1445).
• Append toolchain -isystem include flags to CC/LD (not just CFLAGS) when bootstrapping the built make and pkg-config tools, fixing configure scripts that need toolchain-provided system headers (#1470).
• Symlink a tool's .runfiles alongside it when symlinking tools into the build's bin directory, so hermetic autotools can find their runfiles data (#1434).

Dependencies and toolchains

• Bazel 9 compatibility: load CcSharedLibraryInfo directly from rules_cc and upgrade rules_cc to 0.2.18, so the rules are consumable under Bazel 9 (#1493, #1552).
• The built make tool (4.4 and 4.4.1) is now reproducible across machines, improving cache hit rates (#1543).
• Updated bundled dependency versions, including a new bazel_lib dependency and bumps to rules_python 1.9.0, bazel_skylib, platforms, rules_cc, rules_shell, rules_perl, and rules_rust, mainly to resolve bzlmod version-mismatch warnings and keep lockfiles reproducible (#1462, #1486, #1489, #1482, #1492). The rules_python download URL also moved to the bazel-contrib GitHub org (#1500).

Internal

• Faster builds: copy_dir_contents_to_dir batches its touch -r calls (~22% lower wall-time on darwin/windows example jobs) (#1549).
• Refactors with no behavior change: extracted common framework attributes (#1553), bazelrc-shim plumbing (#1546), data-driven prebuilt-toolchain generation (#1561), and use of rules_cc's msvc-cl config_setting (#1562).
• Removed the legacy Bazel-4-era platform config_settings in favor of @platforms//os:... (#1474).
• Removed the cmake_android example (core Android support is unchanged) (#1471).
• Extensive CI, test-harness, formatting, example, and download-mirror work across many PRs, including the move to a single bazel test phase (#1548), porting examples to bzlmod (#1498), and enabling many third-party examples on Windows.

March 2021:

These rules are now maintained by the community.

Note: After this release we will be bumping the minimum tested version to 4.0.0.

• Added repository rules for downloading prebuilt versions of cmake and ninja rather than relying on system installed tools.

• Added native ninja build rule

• Now builds under the Bazel sandbox rather than in /tmp

• Tidied up the structure of the examples directory

• Deprecated the old rules install_ws_dependency and cc_configure_make

• Autogenerated documentation was added

March 2019:

• Support for versions earlier than 0.22 was removed.

• Tests on Bazel CI are running in the nested workspace

January 2019:

• Bazel 0.22.0 is released, no flags are needed for this version, but it does not work on Windows (Bazel C++ API is broken).

• Support for versions earlier than 0.20 was removed.

• rules_foreign_cc take-aways describing the recent work has been published.

• Examples package became the separate workspace. This also allows to illustrate how to initialize rules_foreign_cc.

• Native tools (cmake, ninja) toolchains were introduced. Though the user code does not have to be changed (default toolchains are registered, they call the preinstalled binaries by name.), you may simplify usage of ninja with the cmake_external rule and call it just by name. Please see examples/cmake_nghttp2 for ninja usage, and WORKSPACE and BUILD files in examples for the native tools toolchains usage (the locally preinstalled tools are registered by default, the build as part of the build tools are used in examples). Also, in examples/with_prebuilt_ninja_artefact you can see how to download and use prebuilt artifact.

• Shell script parts were extracted into a separate toolchain. Shell script inside framework.bzl is first created with special notations:

  • export var_name=var_value for defining the environment variable
  • $$var_name$$ for referencing environment variable
  • `shell_command <space-separated-maybe-quoted-arguments>` for calling shell fragment

  The created script is further processed to get the real shell script with shell parts either replaced with actual fragments or with shell function calls (functions are added into the beginning of the script). Extracted shell fragments are described in commands.bzl.

  Further planned steps in this direction: testing with RBE, shell script fragments for running on Windows without msys/mingw, tests for shell fragments.